Noise considerations can limit the efficiency and maximum size of wind turbines; in part because the blade tip speed must be limited to reduce noise, thus reducing the potential for energy production A major component of wind turbine noise is trailing edge aerodynamic noise (Matthew F. Barone, “Survey of Techniques for Reduction of Wind Turbine Blade Trailing Edge Noise”, Sandia National Laboratories, SAND20011-5252, August 2011, page 8). Trailing edge noise can be reduced to some extent by trailing edge serrations or saw teeth 19 as illustrated in FIG. 1 herein. However, serrations are not effective under all conditions (Barone supra, page 20).